The invention concerns a drilling machine, in particular, a manual drill, whereby optionally (i) the rotating motion of a hollow drive spindle may be transmitted to a drilling tool, or (2) an impact effect may be obtained on the end of an axially movable drilling tool in an impact drill holder by means of an impact bolt guided through the drive spindle.
Manual drills of this type are known (Hilti Operating Instructions for Hammer Drill TE 12, 1981). In the known configurations, in which the rotating drive is effected by means of an electric motor, and the impact bolt is driven pneumatically by a piston reciprocated by an electric drive, special hammer drill tools must be provided for the impact drilling mode of operation; they are designed for positive entrainment. Thus, it is known either to provide longitudinal grooves on the shaft of the tool shaft to engage a plurality of balls provided on the drill spindle, or to design the shaft in a hexagonal form or the like, thereby making it possible to prevent rotation by inserting the tool into a corresponding positive guide, while maintaining axial mobility. Even though these known configurations have a switching position in which essentially only the rotating motion is transmitted, it is a disadvantage in the case of the hammer-type tools that they remain mobile in the axial direction. A further disadvantage is that conventional drilling tools, such as those used in pure drilling machines, may be used only with the insertion of an additional drill chuck, which in turn, has a fastening shaft designed to correspond to the shaft of the impact drilling tools and therefore again cannot be secured satisfactorily in rotation and in the axial direction.
There are further manual drills in which the rotating drive for the drill chuck is combined with a ratchet-like intermediate piece (as described in DE-AS 1155 657), which also provides a certain impact motion, which, however, is not comparable to the intensive, actual impact motion obtained with the afore-mentioned hammer drills. Machines of the last mentioned type may be used (especially for household purposes) for purely drilling work and to a certain extent for work similar to impact drilling, but are not suitable for work requiring an intensive impact action, for example, drilling in concrete or rock.
It is the object of the present invention to design a drilling machine, in particular, a manual drill of the above-mentioned type, so that it is suitable both for use with drilling tools having a smooth shaft and as a hammer drill, without the need for the installation and removal of a drill chuck.